At present the majority of known surgical drains have a tendency to become blocked during a period varying between some minutes and several hours following their installation, according to the anatomical regions and the viscosity of the substances which are to be removed by the drain. It is evident that this obstruction is troublesome since it blocks the functions which have been mentioned hereinabove. The avoidance of such obstruction is thus a constant preoccupation of medical practitioners.
Within the special field of the abdominal, thoractic or pelvic cavity, an obstruction may be produced in three different manners:
since the intra-abdominal, intra-thoracic or intrapelvic organs have a certain physiological mobility, they come into contact with the drain so as to stick to it, and this to a proportionally greater extent if the drain is more frequently subjected to suction to stimulate the removal of the fluids;
the drained substances have a viscosity becoming greater and greater, in particular because of the coagulation and they adhere thus more and more to the internal wall of the drain and end up by blocking it;
by its implantation the inclination of the drain is often not favourable, in particular because of the prone position of the patient. In this case the drain does not benefit from any slope and gravity annuls the syphon effect.
An attempt to provide a drain enabling avoidance of this mediocre operation of well-known drains has been described in the U.S. Pat. No. 3,114,373. In this case there is disclosed a drain set comprising a main tube closed at its distal end and connected to a suction source at its proximal end. The distal end placed within the cavity to be drained (here the gastro-intestinal space) is provided with a row of orifices opening laterally from the tube and through which are drawn in the substances to be removed.
This main tube is flanked by an auxiliary tube which opens out into the main tube entirely at its closed distal end, i.e. beyond the evacuation orifices. At its other end, the auxiliary tube may be left open to the atmosphere, connected to a hypodermic source or to another medication source, or to a bottle containing a saline solution. Air and/or the saline solution may thus flow continuously through the auxiliary tube into the space bounded by the distal end of the main tube in order to be mixed with the drained substances and thus avoid the clogging and deterioration of neighbouring tissues while maintaining within the drain a sufficient air flow.
If the saline solution may to a certain extent avoid coagulation and dissolve the conglomerates forming in the evacuation tube, these difficulties are not avoided if air in place of this solution is introduced into the auxiliary tube. The necessity of a saline solution complicates considerably the drain itself and its employment since the overseeing personnel must renew it, prepare it or obtain it, etc. Furthermore, the saline solution may not be tolerated by the organs surrounding the drain.
On the other hand, in the case of employment on a surgical site, it is out of the question to send ambient air as such into the auxiliary tube since it would be coming from a non-sterile medium. It will thus be necessary to provide an arrangement for sterilizing air or otherwise a source of sterile air which still further complicates the matter, particularly the installation and employment thereof.
The invention has thus as purpose to provide an improved surgical drain which avoids these difficulties and assures permanently the existence of a drain passage without risk of obstruction thereof by coagulation, solid residues or surrounding organs.